JPH08151021A - Method of sterilizing container - Google Patents

Abstract

PURPOSE: To prevent a container from deterioration or discoloration caused by an excessive partial irradiation of an electron beam. CONSTITUTION: A paper cup 2 is first irradiated with an electron beam to obtain the dose distribution with respect to the paper cup 2. And then a shielding structure body 10 for partially shielding the electron beam is provided at a part of the paper cup 2 where the dosage proportion is large. The shielding structure body 10 has a lip end shielding part 12 for shielding the lip end of the paper cup 2 and a side face shielding part 14 for shielding the inner side face of the paper cup 2. The vertical depth of the shielding structure body 10 is made so thick that the paper cup 2 is nearly uniformly irradiated with the dose based on the dose distribution. After such a shielding structure body 10 is attached to the paper cup 2, the paper cup 2 is irradiated with the electron beam to thereby sterilize it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sterilizing containers used for sterilizing containers such as three-dimensional caps and bottles used for foods, medical products and the like.

[0002]

2. Description of the Related Art In recent years, it has been necessary to sterilize pathogenic bacteria and other microorganisms for three-dimensional caps and containers such as bottles used for foods, medical products, etc. in consideration of health and hygiene.
Conventionally, ethylene oxide gas (EOG), hydrogen peroxide (H ₂ O ₂ ) gas, heat, ultraviolet rays, gamma rays, and high-energy electron beams have been used for sterilization of such containers.

However, in the sterilization with a drug such as ethylene oxide or hydrogen peroxide, it is a problem that the drug remains in the container. Further, in the thermal sterilization, if the container is filled with the content, the quality of the content may be deteriorated, and it can be used only in the step before the content is filled.
Moreover, it cannot be applied when the container is made of a heat-sensitive material such as paper or plastic, and the applicable range is limited. Further, in the sterilization by ultraviolet rays, the ultraviolet rays have a limit in the transmission power, and therefore, when sterilizing a container having a complicated shape, it is not possible to sufficiently sterilize a shadowed portion.

Further, in sterilization with gamma rays or high-energy electron beams, since gamma rays or high-energy electron beams have a large penetrating power, when the container is filled with the contents, the gamma rays or the electron beams are also transmitted to the contents through the container. It will result in irradiation. For this reason, the quality of the contents is deteriorated, and such a sterilization method can be used only in the step before filling the contents. Further, since a large amount of X-rays are generated during processing, a dedicated building in which the device is shielded with concrete or the like is required to shield the generated X-rays, and the device becomes large and expensive. . Furthermore, in this case,
It has to be batch-processed in a separate sterilization specialized factory, and it is difficult to incorporate the sterilization process into the container production line.

Therefore, when sterilizing a three-dimensional cap or a container such as a bottle used for foods, medical products, etc., it is necessary to reduce the size of the apparatus as disclosed in JP-A-61-226050. The use of a low-energy electron beam that can be aimed at is being studied.

[0006]

For low energy electron beams, the relationship between the penetration depth of the electron beam and the absorbed dose with respect to the acceleration voltage of the electron beam as shown in FIG. 10 is known. Here, the vertical axis of FIG. 10 represents the ratio of the dose received at the depth when the dose received on the surface of the electron beam irradiated object is 100%, and the horizontal axis of FIG. Mass per unit area of work piece (area density g / m ² )
Represents From the relationship between the penetration depth and the dose, if the density of the object to be processed and a predetermined depth are given to a certain acceleration voltage, the electron beam transmittance at that depth can be known. The penetration depth of the electron beam increases as the electron beam acceleration voltage increases, and is inversely proportional to the density of the object to be processed.
Further, since the electron beam has the property of being scattered by air, the irradiation dose of the electron beam becomes smaller as the distance from the window foil portion from which the electron beam is taken out becomes smaller in the current low energy type electron beam irradiation apparatus. Therefore, when a tall three-dimensional container is irradiated with an electron beam, the dose distribution in the container is not uniform. Therefore, when trying to obtain the required dose in the portion of the container with the smallest dose, the portion of the container with the largest dose will be excessively irradiated with the electron beam, causing the container to partially deteriorate, or When the material of the container is glass, there is a problem that the container is discolored.

The present invention has been made based on the above circumstances, and provides a sterilizing method of a container capable of preventing the container from being deteriorated or discolored by partial excessive irradiation of an electron beam. The purpose is.

[0008]

The invention according to claim 1 for achieving the above object is a sterilizing method of a container, wherein the container is sterilized by irradiating a three-dimensional container with an electron beam. Based on the dose distribution regarding the dose distribution, a shielding means for partially shielding the electron beam is provided in a portion of the container having a large dose ratio, and the electron beam is radiated from above the shielding means so that the container is substantially It is characterized by irradiating a uniform dose.

A container sterilizing method according to a second aspect of the invention is characterized in that, in the first aspect of the invention, the energy of the electron beam is 100 keV or more and 500 keV or less.

According to a third aspect of the invention, in the container sterilizing method according to the first or second aspect of the invention, the material used for the shielding means is a plastic or metal that has a low specific gravity and is resistant to deterioration by radiation. It is characterized by.

[0011]

According to the invention described in claim 1, with the above construction, a shielding means for partially shielding the electron beam is provided in the portion of the container having a large dose ratio based on the dose distribution regarding the container, and the shielding means By irradiating the container with the electron beam from above, it is possible to irradiate the container with a predetermined dose substantially uniformly, so that it is possible to prevent the container from being deteriorated or discolored due to partial excessive irradiation of the electron beam. , The container can be effectively sterilized.

According to the second aspect of the present invention, the energy of the electron beam is 100 keV or more and 500 ke or more by the above constitution.
By setting the voltage to V or less, it is possible to use a compact electron beam irradiation device that employs self-shielding. Therefore, the sterilization process of the container by the electron beam can be incorporated in the process of manufacturing the container, which enables in-line processing.

According to the third aspect of the present invention, the thickness of the shielding means can be increased by using, as the material for the shielding means, a plastic or a metal having a small specific gravity and hardly deteriorated by radiation. Therefore, the mechanical strength of the shielding means can be sufficiently maintained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a container sterilization method according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an electron beam irradiation apparatus used in the container sterilization method, and FIG. 3 is a container sterilization method. It is a figure for demonstrating the paper cup as a to-be-processed object used for a method.

First, the electron beam irradiation apparatus used in the methods of the first to third embodiments will be described. Such an electron beam irradiation device is an Electro Curtain (registered trademark) CB250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd., and as shown in FIG. 2, an electron beam generation unit 50, an irradiation chamber 60, and an irradiation window unit. And 70.

The electron beam generator 50 has a terminal 52 for generating an electron beam and an accelerating tube 54 for accelerating the electron beam generated at the terminal 52 in a vacuum space (acceleration space). In addition, inside the electron beam generator 50, in order to prevent electrons from colliding with gas molecules and losing energy, 1.3 × 10 ⁻⁴ to 1.3 × by a diffusion pump or the like not shown.
The vacuum is maintained at 10 ⁻⁵ Pa. Terminal 52
It has a linear filament 52a that emits thermoelectrons, a gun structure 52b that supports the filament 52a, and a grid 52c that controls thermoelectrons generated in the filament 52a.

The irradiation chamber 60 includes an irradiation space 62 for irradiating an object to be processed with an electron beam. Further, the object to be processed moves in the irradiation chamber 60 from the left side to the right side in FIG. 2 by a conveying means (not shown) such as a conveyor.
The periphery of the electron beam generator 50 and the irradiation chamber 60 is lead-shielded so that X-rays that are secondarily generated during electron beam irradiation do not leak outside.

The irradiation window portion 70 is a window foil 72 made of metal foil.
And a window frame structure 74 that supports the window foil 72 while cooling the window foil 72. The window foil 72 separates the vacuum atmosphere in the electron beam generating unit 50 from the irradiation atmosphere in the irradiation chamber 60, and the irradiation chamber 6 is separated by the window foil 72.
The electron beam is taken out within 0. Ti foil is usually used for the window foil 72.

When a current is applied to the filament 52a to heat it, the filament 52a emits thermoelectrons, which are attracted in all directions by a control voltage applied between the filament 52a and the grid 52c. Of these, only those that have passed through the grid 52c are effectively extracted as electron beams. The electron beam extracted from the grid 52c is accelerated in the acceleration space in the accelerating tube 54 by the acceleration voltage applied between the grid 52c and the window foil 72, then penetrates the window foil 72, and the irradiation window Part 70
The object to be irradiated which is conveyed in the irradiation chamber 60 below is irradiated.

Next, a method of sterilizing the container of the first embodiment will be described. Here, the paper cup 2 is used as the object to be sterilized. The size of this paper cup 2 is
As shown in FIG. 3, the height is 75 mm and the diameter of the mouth is 7
The diameter of the bottom is 0 mm and the diameter of the bottom is 45 mm. When the above electron beam irradiation apparatus is used in the first embodiment, the acceleration voltage is set to 250 kV, and the electron cup is irradiated with the drinking cup of the paper cup 2 standing up.

In the container sterilization method of the first embodiment, first,
The paper cup 2 is irradiated with an electron beam to obtain a dose distribution regarding the paper cup 2. Here, a radiochromic dosimeter as a film dosimeter is used for measuring the absorbed dose. As the dose measuring position, as shown by a small rectangle in FIG. 3, the mouthpiece P ₁ of the paper cup 2, the inner side surface P ₂ just below the mouthpiece, the inner side surface P ₃ 40 mm below the mouthpiece, And four points on the inner surface P ₄ immediately above the bottom surface. The measurement results are shown in FIGS. 3 and 4. That is, the absorbed dose is
36.9 kGy at position P ₁ and 22.7 kG at position P ₂ .
y, 15.8 kGy at position P ₃ , and 1 at position P ₄ .
It was 2.4 kGy.

By the way, the dose (D value) required for sterilizing a certain number of bacteria to kill 90% of the original number is B. pumilus (spores) E-601 which is an index in radiation sterilization. About 2kG
It is y. It is considered that about several bacteria are attached to a normal film, paper or the like per cm ² , but here, for the sake of safety, it is assumed that there are 10 ² viable bacteria. When the initial number of bacteria is about 10 ² , the sterilization assurance level (SAL) is generally said to be a survival rate of 10 ^-6 %. Therefore, by irradiating a dose of 8D, that is, 8 × 2 = 16 kGy, sterilization of sterilization grade can be surely performed.
However, in general, effective sterilization can be performed by irradiating a dose of at least about 10 kGy. On the other hand, when the object to be processed is made of a material that is easily deteriorated by radiation, if the object to be processed is irradiated with too much dose, the object to be processed may deteriorate or the surface may be discolored. .

Therefore, in the first embodiment, one paper cup 2 is added.
In order to irradiate the dose of about 0 kGy substantially uniformly, a shielding structure (shielding means) that partially shields the electron beam with which the paper cup 2 is irradiated is used. According to the dose distribution for the paper cup 2 obtained by the above measurement, the absorbed dose decreases from the mouth of the paper cup 2 to the bottom surface, and the inner surface P ₄ just above the bottom surface is reduced.
And the desired dose (10 kGy) is about 12.4 kGy
Is. From this, as the shielding structure 10, as shown in FIG.
As shown in FIG. 4, a structure having a drinking mouth shield 12 that shields the mouth of the paper cup 2 and a side shield 14 that shields the inner surface of the paper cup 2 is used. . The mouthpiece shielding portion 12 is formed in a cylindrical shape having an inner diameter similar to the diameter of the mouthpiece of the paper cup 2. The side shields 14 are formed to have substantially the same shape as the side surfaces of the paper cup 2, and the thickness in the up-down direction becomes thicker toward the portion corresponding to the drinking mouth of the paper cup 2. Shield structure 1
Specifically, the thickness of 0 in the vertical direction is based on the dose distribution regarding the paper cup 2 so that the absorbed doses at the positions P ₁ , P ₂ and P ₃ are the same as the absorbed dose at the position P ₄ . Ie about 1
It is defined as a thickness such that it becomes 2 kGy. Aluminum is used as the material of the shielding structure 10.

Next, the shielding structure 10 is inserted into the paper cup 2 by inserting the side shielding portion 14 into the paper cup 2.
Attach to Then, the paper cup 2 to which the shielding structure 10 is attached is placed on the conveyor of the electron beam irradiation device, and the electron beam is irradiated in the irradiation chamber 60.

The present inventors measured the absorbed dose for the paper cup 2 irradiated with this electron beam. The measuring method and the measuring position are the same as in the case where the shielding is not performed. FIG. 4 shows the measurement results. That is, the absorbed dose is 12.0 kGy at the mouth P ₁ , 12.5 kGy at the inner surface P ₂ just below the mouth, 10.4 kGy at the inner surface P ₃ 40 mm below the mouth, just above the bottom. 11.8 on inner surface P ₄
It was kGy. Therefore, 10kG for paper cup 2
It can be seen that an effective sterilization treatment can be carried out because a dose of about y can be irradiated substantially uniformly.

In the container sterilization method of the first embodiment, a shielding structure for partially shielding the electron beam is provided on the portion of the paper cup having a large dose ratio based on the dose distribution regarding the paper cup, and the shielding is performed. By irradiating the structure with an electron beam, it is possible to irradiate the paper cup with a predetermined dose almost uniformly, so it is possible to prevent the paper cup from being deteriorated or discolored by radiation. While you can
The paper cup can be effectively sterilized.

In the first embodiment, the electron beam accelerating voltage is set to 250 kV, so that a low energy type electron beam irradiating device which is self-shielding and compact can be used. Therefore, the sterilization treatment of the paper cup by the electron beam can be incorporated in the manufacturing process of the paper cup, and the in-line can be realized.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a diagram for explaining the container sterilization method according to the second embodiment of the present invention, and FIG. 6 is a diagram for explaining a vial bottle as an object to be used in the container sterilization method.

In the second embodiment, a vial bottle 4 is used as the object to be processed. The vial 4 is a glass container as shown in FIG. The vial 4 is filled with a rubber stopper 6 at the entrance thereof and further covered with an aluminum cap 8 from above. By crimping the aluminum cap 8 and closing the opening on the upper surface of the aluminum cap 8, the contents can be sealed with high accuracy. In the second embodiment, the case where the surface sterilization of the vial bottle 4 is performed in a state where the upper surface of the aluminum cap 8 is not opened is considered. In this case, the aluminum cap 8 can be regarded as a kind of shielding means, and in particular, effective sterilization in the gap between the vial 4 and the aluminum cap 8 is an important issue. When the electron beam irradiation apparatus shown in FIG. 2 is used in the second embodiment, the accelerating voltage is set to 250 kV as in the first embodiment, and the vial 4 is tilted sideways and rotated. Irradiate with electron beam.

In the container sterilization method of the second embodiment, first,
The dose distribution regarding the vial 4 is obtained by irradiating the vial 4 with an electron beam. Here, a radiochromic dosimeter is used for measuring the absorbed dose, as in the first embodiment.
As for the dose measuring position, as shown in FIGS. 5 and 6, the upper surface P _{5 of} the aluminum cap 8, the gap P ₆ between the vial 4 and the aluminum cap 8, and the side surface P _{7 of the} vial 4.
It has three points. The measurement result is shown in FIG. That is, the absorbed dose is 100 kGy at position P ₅ and P _{6 at} position P _6.
Was 4.8 kGy and at position P ₇ was 50.8 kGy.
The dose is 100 kGy on the upper surface P ₅ of the aluminum cap 8.
The reason for this is that the vial 4 is tilted sideways and rotated, so that the upper surface of the aluminum cap 8 is constantly exposed to the electron beam.

From this measurement result, in order to irradiate the vial container 4 with a substantially uniform dose, the absorbed dose at the side surface P ₇ of the vial container 4 is measured at the gap P ₆ between the vial container 4 and the aluminum cap 8. It is understood that the dose should be reduced to the same level as the absorbed dose, that is, about 10%. Therefore, in the second embodiment, as the shielding structure 20, as shown in FIG. 5, a guide portion 22 for guiding the vial 4 by sandwiching the mouth portion thereof from the vertical direction and a guide portion 22 parallel to the guide portion 22. A structure having a side plate 24 provided on the above, a guide portion 22, and a titanium foil 26 stretched on the upper side of the side plate 24 is used. Guide part 2
In No. 2, an aluminum material is used as a substrate, and in order to prevent the glass of the vial bottle 4 from being scratched and to make the vial bottle 4 slip easily, a material coated with silicone as a radiation resistant material is used. The side plate 24 uses titanium foil or aluminum foil. In addition, this shielding structure 2
0 means that the vial 4 rolls naturally, as shown in FIG.
Is inclined so that the depth direction is high and the front direction is low. With such a structure, the shielding structure 20 shields the electron beam only from the body portion excluding the mouth portion of the vial 4. On the other hand, as for the thickness of the titanium foil 26, the dose on the side surface P ₇ of the vial 4 is 1 as shown in FIG.
The thickness is set to 0%. According to the curve showing the relationship between the penetration depth and the dose shown in FIG. 10, when the acceleration voltage of the electron beam is 250 kV, the titanium foil has an areal density of 500 g / m ^{2 in} order to make the dose 10%. You can see that The density of titanium is about 4.5 g / c
Since it is m ³ , the thickness of the titanium foil 26 is 500 (g / g).
m ² ) ÷ 4.5 (g / cm ³ ) = 111 (μm). An aluminum foil may be used instead of the titanium foil 26. However, in this case, since the density of aluminum is about 2.7 g / cm ³ , the thickness of the aluminum foil must be 185 μm.

Next, the shielding structure 20 is mounted in the irradiation chamber 60 below the window foil 72 in the electron beam irradiation device. Since it is necessary to irradiate the gap between the vial 4 and the aluminum cap 8 with a dose of about 10 kGy,
For example, the beam current of the electron beam irradiation device is set to about twice that in the case where the above shielding is not applied. Then vial 4
Is placed at a predetermined position on the shielding structure 20, the vial bottle 4 naturally rolls down and the vial container 4 is irradiated with an electron beam.

The present inventors measured the absorbed dose for the vial 4 irradiated with this electron beam. The measuring method and the measuring position are the same as in the case where the shielding is not performed. The measurement result is shown in FIG. That is, the absorbed dose is 200 kGy on the upper surface P ₅ of the aluminum cap 8 and the vial 4
The gap P ₆ between the aluminum cap 8 and the aluminum cap 8 was 10.3 kGy, and the side face P ₇ of the vial 4 was 10.5 kGy. Therefore, the absorbed dose is about 10 kGy both in the gap P ₆ between the vial 4 and the aluminum cap 8 and in the side surface P _{7 of} the vial 4, and the dose can be irradiated substantially evenly on the surface of the vial 4. It turns out that effective sterilization can be performed.

On the upper surface P ₅ of the aluminum cap 8, the absorbed dose is considerably large at 200 kGy, but in the second embodiment, the mouth of the aluminum cap 8 is not open, and since aluminum is not easily deteriorated by radiation, There is no problem. However, when the mouth of the aluminum cap 8 is open, it is necessary to shield the upper surface of the aluminum cap 8 to suppress the absorbed dose to about 10 kGy in order to prevent the rubber stopper 6 from being deteriorated by radiation. is there.

In the container sterilization method of the second embodiment, a shielding structure for partially shielding the electron beam is provided on the portion of the vial having a large dose ratio based on the dose distribution regarding the vial, and the shielding is performed. By irradiating the vial with an electron beam from above the structure, it is possible to irradiate the vial with a predetermined dose substantially uniformly, so that the glass, which is the material of the vial, is deteriorated or discolored by the radiation. And the vial can be effectively sterilized. The other effects are similar to those of the first embodiment.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a view for explaining the container sterilization method according to the third embodiment of the present invention.

Also in the third embodiment, the case where a vial bottle is used as the object to be processed and the surface sterilization of this vial bottle is considered. This vial is the same as that used in the second embodiment. When the electron beam irradiation apparatus shown in FIG. 2 is used in the third embodiment, the accelerating voltage is set to 250 kV as in the second embodiment, but the point of irradiating the electron beam with the vial set up is the point. Different from the second embodiment.

In the container sterilization method of the third embodiment, first,
The dose distribution for the vial 4 is measured. Here, the measuring method and the measuring position of the absorbed dose are the same as those in the second embodiment. FIG. 9 shows the measurement results. That is, the absorbed dose is 100 kGy on the upper surface P ₅ of the aluminum cap 8,
3.8 in the gap P ₆ between the vial 4 and the aluminum cap 8.
kGy was 37.5 kGy on the side surface P ₇ of the vial 4.

From this measurement result, in order to irradiate the vial 4 with a substantially uniform dose, as in the second embodiment,
The absorbed dose on the side surface P ₇ of the vial 4 is
It is understood that the dose may be reduced to the same level as the absorbed dose in the gap P ₆ between the aluminum cap 8 and the aluminum cap 8, that is, to about 10%. Then, in the third embodiment, the shielding structure 30 is considered in consideration of irradiating the electron beam in the state where the vial 4 is set up.
As shown in FIG. 8, a structure having a cylindrical side surface and a hole formed in the upper surface is used. This shield structure 3
0 is made using an aluminum plate. Shield structure 30
Is almost the same as the height from the bottom of the vial 4 to the lower end of the aluminum cap 8 when the vial 4 is covered with the aluminum cap 8, and the diameter of the hole formed on the upper surface is
It is approximately the same as the diameter of the mouth portion of the vial 8. Also,
The shield structure 30 has a structure that can be opened and closed to the left and right. As a result, the shielding structure 30 is opened and the vial bottle 4 is opened.
The vial 4 can be easily housed in the shielding structure 30 except for the aluminum cap 8 by simply putting the inside. On the other hand, the thickness of the aluminum plate is set to a thickness such that the dose at the side surface portion P ₇ of the vial container 4 is 10%, that is, 185 μm from FIG.

Next, the vial 4 housed in the shielding structure 30 is placed on the conveyor of the electron beam irradiation device, and the electron beam is irradiated in the irradiation chamber 60. Where vial 4
Since it is necessary to irradiate a dose of about 10 kGy to the gap between the aluminum cap 8 and the aluminum cap 8, for example, the conveyor speed of the electron beam irradiation device is set to a slower one-third to one-half when the shielding is not performed. are doing.

The present inventors measured the absorbed dose for the vial 4 irradiated with this electron beam. The measuring method and the measuring position are the same as in the case where the shielding is not performed. FIG. 9 shows the measurement results. That is, the clearance P ₆ between the vial 4 and the aluminum cap 8 and the side surface P _{7 of the} vial 4.
In both cases, the absorbed dose is about 10 kGy, and it can be seen that the vial 4 is irradiated with the dose substantially uniformly.
Therefore, even in the container sterilization method of the third embodiment, similarly to the second embodiment, the glass as the material of the vial is prevented from being deteriorated or discolored, and the vial is effectively It can be sterilized. In addition, other effects are
This is similar to the first embodiment.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention. In each of the above-mentioned examples, the case where titanium or aluminum is used as the material used for the shielding structure has been described. However, as the shielding material, in general, the specific gravity is small, and the plastic is not easily deteriorated by radiation,
It is desirable that it is metal or its equivalent. By making the specific gravity small in this way, the thickness of the shielding structure made of the material can be made as thick as possible, so that the mechanical strength of the shielding structure can be sufficiently maintained.

In each of the above-mentioned embodiments, the shielding structure is always exposed to the electron beam, so that the temperature of the shielding structure may rise. Therefore, in such a case, it is desirable to cool the shield structure by flowing cooling water or the like.

Further, in each of the above embodiments, the case where the acceleration voltage of the electron beam irradiation apparatus is set to 250 kV and the electron beam is irradiated to the object to be processed has been described, but the acceleration voltage is in the range of 100 kV to 500 kV. It is desirable to set in. Within such a range, an electron beam irradiation apparatus adopting self-shielding can be used, and the container sterilization treatment according to the present invention can be incorporated in the container manufacturing process, and in-line processing is possible.

[0045]

As described above, according to the first aspect of the invention, the shielding means for partially shielding the electron beam is provided on the portion of the container having a large dose ratio based on the dose distribution regarding the container. By irradiating the container with the electron beam from above, it is possible to irradiate the container with a predetermined dose substantially uniformly, so that the container is deteriorated or discolored by partial overirradiation of the electron beam. It is possible to provide a method for sterilizing a container, which can prevent the occurrence of the above and effectively sterilize the container.

According to the second aspect of the invention, since the electron beam energy is set to 100 keV or more and 500 keV or less, it is possible to use a compact electron beam irradiating device which employs self-shielding. It is possible to provide a container sterilization method in which the sterilization process of the container by a wire can be incorporated in the manufacturing process of the container and which can be in-lined.

According to the third aspect of the present invention, the thickness of the shielding means can be increased by using, as the material used for the shielding means, a plastic or metal that has a small specific gravity and is not easily deteriorated by radiation. It is possible to provide a method for sterilizing a container that can sufficiently maintain the mechanical strength of the shielding means.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method of sterilizing a container which is a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electron beam irradiation apparatus used for the method of sterilizing the container.

FIG. 3 is a diagram for explaining a paper cup as an object to be used for the method of sterilizing the container.

FIG. 4 is a diagram showing a measurement result of a dose at each part when the paper cup is irradiated with an electron beam.

FIG. 5 is a diagram for explaining a container sterilization method that is a second embodiment of the present invention.

FIG. 6 is a diagram for explaining a vial as an object to be processed used in the method for sterilizing the container.

FIG. 7 is a diagram showing measurement results of dose in each part when the vial is irradiated with an electron beam.

FIG. 8 is a diagram for explaining a container sterilization method that is a third embodiment of the present invention.

FIG. 9 is a diagram showing a measurement result of a dose in each part when a vial as an object to be used for the method of sterilizing the container is irradiated with an electron beam.

FIG. 10 is a diagram showing a relationship between penetration depth of an electron beam and absorbed dose.

[Explanation of symbols]

 2 Paper cup 4 Vial bottle 6 Rubber stopper 8 Aluminum cap 10, 20, 30 Shielding structure 12 Shielding part for drinking mouth 14 Shielding part for side 22 Guide part 24 Side plate 26 Titanium foil 50 Electron beam generating part 52 Terminal 52a Filament 52b Gun Structure 52c Grid 54 Accelerator tube 60 Irradiation chamber 62 Irradiation space 70 Irradiation window part 72 Window foil 74 Window frame structure

Claims (3)

[Claims] 1. A container sterilization method for sterilizing a three-dimensional container by irradiating the container with an electron beam, wherein the electron is applied to a portion of the container having a large dose ratio based on a dose distribution regarding the container. A method of sterilizing a container, characterized in that a shielding means for partially shielding a ray is provided, and the electron beam is applied from above the shielding means to irradiate the container with a substantially uniform dose. 2. The energy of the electron beam is 100 ke
The method for sterilizing a container according to claim 1, wherein the method is V or more and 500 keV or less. 3. The method for sterilizing a container according to claim 1, wherein the material used for the shielding means is a plastic or a metal having a small specific gravity and hardly deteriorated by radiation.